Question: What is the head of government of north Rhine -Westphalia that has start time is 1956-2-20?
Paraphrase: Who was the head of the government of north Rhine-Westphalia beginning in 1956-2-20?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q1198 p:P6 ?s . ?s ps:P6 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1956')) }